DETECTIVE  POWER  OF  THE  MICROSCOPE. 
47 
Dr.  Pereira  first  impressed  on  the  attention  of  pharmaceutists 
the  value  of  this  instrument  for  discriminating  between  the  nu- 
merous varieties  of  starch  which  are  oifered  to  the  public  for 
domestic  purposes,  under  an  equal  variety  of  names  ;  but  it 
remained  for  Dr.  Hassal  to  show  its  unlimited  valuable  appli- 
cations. 
The  conclusions  that  may  be  drawn  from  the  Lancet  commis- 
sioner's laborious  researches  are,  that  the  solid  portions  of  all 
organised  structures  present  to  the  eye,  when  aided  by  the  mi- 
croscope, such  distinguishing  characteristics,  that,  by  an  expe- 
rienced observer,  they  can  be  referred  to  their  respective  origins ; 
and  that  when  even  these  portions  are  in  a  state  of  minute  sub- 
division, the  form  of  the  cells,  the  shape  of  the  starch  granules, 
and  the  condition  of  the  spiral  vessels,  and  other  indications, 
afford  an  equally  accurate  result. 
To  assert  that  Dr.  Hassal  has  never  arrived  at  an  erroneous 
conclusion  in  his  investigations,  would  be  to  ascribe  to  him  some- 
thing more  than  human  ;  but  to  state  that  his-  results  are  sur- 
prisingly accurate,  would  be  within  the  limits  of  truth  ;  to  which 
statement  even  the  victims,  as  no  doubt  they  consider  themselves, 
of  his  indefatigable  and  ruthless  microscopic  skill,  have  repeat- 
edly borne  testimony. 
As  this  paper  is  written  for  the  student,  and  not  for  the  ini- 
tiated in  these  matters,  we  shall  here  briefly  indicate  the  method 
by  which  skill,  when  aided  by  perseverance,  may  be  acquired  in 
detecting  the  adulteration  of  drugs,  by  microscopical  observation. 
It  is  unnecessary  to  describe  the  construction  of  the  microscope, 
as  it  is  an  instrument  that  most  persons  are  familiar  with,  and  a 
description  of  it  may  be  found  in  many  standard  works ;  but  it 
may  be  observed  that  the  instrument  necessary  for  this  purpose 
should  possess  a  magnifying  power  from  200  to  400  diameters. 
We  shall  assume,  to  illustrate  the  method,  that  a  sample  of 
suspected  powdered  rhubarb  has  been  taken  for  examination ; 
but  before  the  investigator  can  pronounce  an  opinion,  or  form  a 
judgment  of  the  suspected  sample,  it  is  necessary  that  he  should 
be  well  acquainted  with  the  characteristics  of  powdered  rhubarb 
of  authenticated  genuineness,  which  he  can  readily  prepare  for 
himself. 
It  is  by  a  comparative  examination  of  the  genuine  and  the  adul- 
